Light control films are a material that gives a light transmittance varied in accordance with whether or not an electric field is applied thereto, so as to be able to adjust the incident light amount. Known is, for example, a light control film being obtained by sandwiching a light control layer between transparent electroconductive resin substrates, the light control layer being obtained by dispersing a light control suspension in which a light control particles are dispersed, into a resin matrix, the light control particles responding to an electric field. This light control film is a film in which fine droplets of the light control suspension in which the light control particles are dispersed, are dispersed in the resin matrix, which is cured by irradiation with ultraviolet rays. In this light control film, the light control particles absorb, scatter or reflect light by Brownian motion in the state that no electric field is applied thereto; thus, incident light into the film cannot penetrate through the film. When an electric field is applied thereto, the light control particles are oriented in the direction parallel to the electric field by the polarization of the particles; thus, incident light to the film can penetrate through the film. In such a way, in a light control film, the amount of transmitted light is adjusted in accordance with the response of light control particles therein to an electric field (see Japanese Patent Application National Publication No. 8-503314).
As such a light control film, known is a film in which a light control layer is formed directly between two glass plates. For example, Japanese Patent Application National Publication No. 8-503314 discloses, in an example thereof, a light control film obtained by forming a light control layer about 100 μm in thickness on a polyester sheet 127 μm in thickness, curing the light control layer, transferring the cured layer onto a glass plate, about 3 mm in thickness, covered with ITO, peeling off the polyester sheet and then sandwiching the light control layer between the glass plate and another glass plate equivalent thereto. Japanese Patent Application Laid-Open (JP-A-) No. 9-113939 discloses, in an example thereof, a light control film formed by forming a light control layer so as to the thickness is about 50 μm, onto each of two glass substrates each coated with ITO, and then integrating these members into one unit in a vacuum. However, such a method of forming a light control layer directly onto glass plates is poor in workability, for example, for the formation of the layer onto glass substrates having a large area. Moreover, the film thickness of the light control layer is not easily made uniform; thus, it is difficult to yield a light control film which is uniform as a whole and has an excellent light control performance.
As a film for improving this film, known is a light control film obtained by applying a light control material onto each of polyester films 125 μm in thickness, having a surface on which an ITO transparent electrode film is formed, so as to yield two films with the light control material, and then stacking the two films onto each other (see Examples of JP-A No. 2002-189123). Additionally, JP-A Nos. 2005-300962, 2006-64832 and others give descriptions over a wide scope which include the following content: in a case where transparent substrates between which a light control layer is to be sandwiched are each a glass, the thickness is preferably from 1 to 15 mm; and in a case where the substrates are each a polymeric film, the thickness is preferably from 10 to 1000 μm. However, examples thereof disclose only a method of forming a light control layer directly between glass plates, as described in JP-A No. 9-113939. The use of polymeric films as substrates is neither specifically described nor sufficiently investigated in the actual circumstances.